Topical
Antibiotics Are Effective in Bacterial Conjunctivitis

Question

Does the use of empiric topical antibiotic therapy shorten the clinical
course of acute conjunctivitis?

Clinical
Bottom Lines

Acute conjunctivitis is a self-limited disease, although topical antibiotic
therapy with polymyxin-bacitracin shortens the duration of clinical
disease and enhances eradication of the causative organism from the
conjunctiva.

Among patients treated with polymyxin-bacitracin, 62% showed clinical
cure at 3-5 days, whereas only 28% of those treated with placebo were
cured (ARR=34%, NNT=3).1 There was no difference in
clinical cure rate at 8-10 days.

The percentage of patients with negative cultures at 3-5 days was 71%
for those treated with antibiotics and 19% for those given placebo (ARR=52%,
NNT=2). This difference was still present at 8-10 days.

Summary of Key Evidence

In this randomized, double blinded, multi-center study, 116 patients
were randomized to a 7 day course of either polymyxin-bacitracin ointment
or placebo. At one center, patients were randomized after cultures become
positive for either S. pneumoniae or H. influenzae were also treated
with systemic antibiotics for associated bacterial infections. Placebo
and control groups had essentially similar characteristics at the onset
of the study.1

Outcomes were measured during therapy (3-5 days) and at the conclusion
(8-10 days) of treatment. Outcomes included clinical cure and
bacteriologic cure (i.e. eradication of the organism on culture.).

No statistically significant difference in clinical cure was noted at
the second visit, although no power calculation was made to determine
of the sample size was large enough to detect a difference. At
day 3-5, there was a statistically significant degree of clinical cure
in those receiving antibiotics. There was an impressive difference
in bacteriologic cure both at day 3-5, and at the conclusion of treatment.

Concerns regarding the validity of the data offered in the study include
the following: 1) A fairly small sample size of approximately 30 patients
per group. 2) The fact that some patients were not randomized
until after cultures had come back positive. 3) Analysis of the data
in groups of patient different than the groups to which they were randomized.
Data was analyzed in 3 groups, including one for patients who also received
oral antibiotics. This group should either have been excluded
from the study, or randomized with stratification taking this variable
into account. Nevertheless, examination of the data specifically
related to the treatment of bacterial conjunctivitis with topical antibiotics
reveals it to most likely be significant.

Additional
Comments

An earlier controlled study by the same author showed that 42% of
cases are caused by H. influenzae, 12% by S. pneumoniae, 20% by adenoviruses,
with 28% culture negative.2

The best clinical clues as to the presence of bacterial versus viral
conjunctivitis are as follows: a) associated otitis media is suggestive
of bacterial disease and warrants oral antibiotic therapy; b) associated
pharyngitis is highly suggestive of adenoviral conjunctivitis (Positive
Likelihood Ratio of 9); c) the presence of purulent exudate is somewhat
suggestive of bacterial conjunctivitis. (Positive Likelihood Ratio of
2).2

Neonatal conjunctivitis involves a different spectrum of organisms
(i.e. Chlamydia trachomatis and Neisseria gonorrhea) requires a culture
and systemic antibiotics: the this article is not relevant to that patient
population.